In LTE (Long Term Evolution), each LCH (Logical Channel), in other words, each EPS (Evolved Packet System) bearer is operated under PER (Prioritized Bit Rate) control in MAC (Media Access Control) layer in an uplink, so that a transmission rate at a certain level can be guaranteed (see Non-Patent Document 1).
In LTE, in a case where such PBR control is not being performed and where there are two LCHs different in priority, for example, data for the LCH at the lower priority cannot be transmitted unless all data for the LCH at the higher priority is transmitted.
In short, the foregoing PBR control aims at avoiding such a situation (Starvation).
Specifically, in order to perform such PBR control, it is necessary in the MAC layer to manage the costs (Bj) of the respective LCHs, and to execute the following steps in a TTI (Transmission Time Interval) in which the allocation of new transmission resources specified by “UL grant” takes place.
In step 1, the aforementioned new transmission resources are allocated to data for LCHs having positive costs in descending order of the priority.
In step 2, in the LCH to which the aforementioned new transmission resources are allocated, the cost of the LCH is decremented by the data volume of the MAC-SDU corresponding to the transmission resources allocated.
In step 3, if new transmission resources still allocatable remain after completion of the allocation of transmission resources for the data for LCHs having the positive costs, the transmission resources are allocated for data for LCHs having negative costs in descending order of the priority.
Meanwhile, CA (Carrier Aggregation) specified in LTE Release-10 is capable of achieving high throughput through simultaneous communications using CC(Component Carrier) #1 and CC#2 under the same radio base station eNB as illustrated in FIG. 7(a).
On the other hand, in LTE Release-12, “Inter-node UP aggregation” to which the CA in LTE Release-10 is extended is under considerations (see Non-Patent Document 2). “Inter-node UP aggregation” is intended to achieve high throughput through simultaneous communications using CC#1/CC#2 under different radio base stations eNB#1/eNB#2 as illustrated in FIG. 7(b). For example, if all the CCs cannot be accommodated in a single radio base station eNB, it is necessary to perform “Inter-node UP aggregation” in order to achieve the throughput comparable to that of LTE Release-10